What Is Hair?

Hair is a keratinous outgrowth that appears on the human skin (except for lips, fingertips, palms of the hands and feet, the glans penis, and labia minora). Each hair is composed of non-living cells filled with a protein called keratin. It is also made up of a very light, brittle material called collagen. Hair grows from follicles that penetrate the outermost layer of the skin, the epidermis. Hair strands then grow up through the follicle to protrude above the epidermis.

The shape of a hair’s follicle is what determines how straight or curly a person’s hair will be. Straight hair is produced by follicles that are roughly oval in cross-section. Curly hair is produced by follicles with a dominant C-shaped curve. A person’s strands of hair can be wavy, curly, or kinky, and their color can range from dark to blonde to salt-and-pepper.

Most of the atoms in our hair are held together by hydrogen bonds. The strong disulfide bonds in a hair’s protein chains give it its strength, and the hydrogen bonds that make it flexible are found primarily between polar amino acids. Because of this, hair can stretch a lot before it breaks. This flexibility also gives it its characteristic bounce and lustre.

Hair consists of two types of fibers: vellus hairs, which are soft, fuzzy and short and are found everywhere on the body, and terminal hairs, which are thicker and coarser and located mainly on the head. Vellus hairs are essentially dead cells that have been filled with keratin, while terminal hairs are follicles that produce living, mitotic cells and then transform into the non-living keratin we know as hair.

As a character’s hair grows out of the scalp, it becomes progressively longer and thicker until it eventually gets to a point where it can be combed and styled. In many cultures, the length of a person’s hair is associated with his or her social class and can be used as an indicator of biological sex, age, and ethnic ancestry. In addition, a person’s hairstyle can provide clues about the person’s personality, beliefs, and culture.

While some people’s hair can be very attractive, others’ hair can be a source of embarrassment or distress. This may be due to the genetic predisposition to baldness or other health issues. Hair problems are a common occurrence and may include split ends, breakage, graying of the hair, thinning, traction alopecia, psoriasis, or trichotillomania.

Although some of the things that influence a person’s hair can be controlled, many other factors are not. These may include hormones, nutritional deficiencies, autoimmune diseases, and illnesses that affect the hair follicle. Hair is also affected by external influences such as sunlight, chemicals, and pollution.